It is well known in motor vehicles to mount an air bag beneath the instrument panel for deployment through an opening in the instrument panel. The opening in the instrument panel is conventionally closed by a deployment door which is hingedly mounted on the instrument panel by a hinge defining a transversely extending hinge axis. It is also known in the prior art that the hinge may be defined by a flexible or elastic strap allowing door opening to facilitate the deployment of the air bag through the opening.
Prior to opening, the door must be held in place securely enough to prevent tampering. On the other hand, when the air bag is deployed, the resistance force holding the door closed should be as small as possible. It is known to use either skin lock or locking bolts to secure the door. In these designs, the skin lock or the locking bolts will be broken by the pressure built up in the bag and the deployment door will then be free to hinge open and deploy the bag.
It is also known to use a latch to hold the door closed and a gas pressure operated cylinder and piston device to release the latch when the bag is deployed, using the gas pressure fed through a special passage from the air bag inflater to operate the release mechanism. While the concept of using a latch for the deployment door is a desirable feature, the separate system for releasing the latch adds complexity to the air bag system.